Rate-of-climb indicator or the like for aircraft



Nov. 23, 1943. R. ROUDNICKY RATE-OF-CLIMB INDICATOR OR THE LIKE FORAIRCRAFT Filed Aug. 17, 1940 v 4 INVEINTORI.

ATTOR Yl.

'atenteci Nov. 23, 1943 RATE-OF-CLIMB INDICATOR OR THE LIKE FOR'ABWCRAFT Rudolf Roudnicky, Prague, Czechoslovakia; vested in. the AlienProperty Custodian Application August 17, 1940, Serial No. 353,148 InCzechoslovakia. April 7, 1938 2 Claims.

This invention relates to rate-of-climb indicators and the like foraircraft, of the type in which the barometric pressure mechanism, suchas an aneroid capsule or diaphragm, is contained in a heat-insulatedcasing and communicates with the outer atmosphere through a tube and inwhich the interior of the casing itself communicates with the outeratmosphere through a capillary tube. Altimeters of this type suffer fromthe disadvantage that, if the aircraft changes its altitude too rapidlythe pressure within the heat-insulated casing cannot become equal tothat of the outer atmosphere sufiiciently quickly, so that asatmospheric pressure also prevails inside the barometric pressuremechanism, the latter, which in view of the sensitivity requiredconsists of extremely thin sheet metal, becomes damaged.

The object of the present invention is to overcome this disadvantage,and this is achieved by providing the interior of the heat-insulatedcasing, in which the aneroid capsule or the like is arranged with avalve which is automatically opened by a movable part of thetransmission leverage of the altimeter, or directly by the wall of theaneroid capsule, or by an auxiliary aneroid capsule, as soon as acertain maximum allowable, value of difference of pressure between theouter atmosphere and the interior of the casing is reached, so that thepressure prevailing in the casing becomes, through such valve, at onceequal to that of the outer atmosphere. This arrangement isadvantageously supplemented by a filter plug by means of which theeffect of the rapidly changing pressure of the outer atmosphere on theaneroid capsule or the like is also retarded.

In the drawing, in which an embodiment of the invention is illustrated,with the required details, by way of example,

Fig. 1 is a vertical section on the line 1-1 of Fi Fig. 2 is a sectionon the line II-II of Fig. 1,

Fig. 3 is a plan view of the altimeter scale, and

Fig. 4 is a vertical section of a modified embodiment.

Referring to the drawing, the altimeter consists of a known,heat-insulated, double-walled, evacuated casing I, which is arranged inthe cylindrical protective casing 2 and contains a known form ofbarometric pressure mechanism such as an aneroid capsule 3, whichcommunicates with the outer atmosphere through a small tube 4 by way ofthe free space in the casing 2 and the tubular fitting 5. This aneroidcapsule acts, through a suitable lever mechanism 6, a gear section I andgear wheel 8, upon the shaft 9 of a pointer or indicator III, whichmoves over a scale II provided on the upper side of the enclosedaltimeter.

According to the invention the space l2 within the'casing I communicateswith the outer at mosphere through a capillary tube l3 in known mannerto enable a gradual equalisation of the difference of pressure, as wellas through a relief tube M of relatively large bore which opens into anauxiliary casing l5 having a non-return valve comprising a valve body l6which is normally pressed down to its seat by a spring I1 and ispositively connected with a movable part of the altimeter, for examplewith the gear sector 'I (Fig. 2) by a control rod IS. The valve bodymay, however, also be connected with some other part, for example it maybe connected direct with the wall of the aneroid capsule 3, or with thewall of an auxiliary aneroid capsule, the hollow interior of whichcommunicates directly with the outer atmosphere as shown for example inFig. 4. In the embodiment shown in Fig. 1 and Fig. 2 the control rod I9is connected with the gear sector I and with the valve body 16, with theprovision of a certain amount of play in such a manner that the valvebody only opens or moves against the action of the spring l1, if thesector I has performed the maximum possible swing, for example from 0 to20 on the scale II, this swing also corresponding to the highestpermissible pressure load of the aneroid capsule 3. As shown in Fig. 1,the casing l is preferably closed by a fiat closing wall through whichpass the pointer shaft 9, the tube 4, the capillary tube l3, and therelief tube Hi.

If the aircraft descends by a small amount the difference in pressurewill not reach the danger value, and the pointer I 0 will not reach thegraduation 20, but if the aircraft descends from a considerable heightto a relatively low altitude within a very short period, the differenceof pressure may exceed that limit, so that the valve [5 will be openedas soon as the pointer reaches the graduation 20 on the scale II, andthe pressure inside the casing I will at once become equal to that ofthe outer atmosphere, so that the pointer ill will return to theposition 0.

The correct adjustment of the control rod 19 is such that the pointer l0points to the maximum graduation 20 of the scale in the first instance,and the positive connection of the control rod with the valve body l6effected in that position. As long as the pointer l0 does not reach thevalue 20 on t'he scale II, the valve IE will not be opened.

According to a. feature of the invention, a filter plug 2| of a suitableporous material, for example pumice stone or the like, is arranged inthe tubular fitting of the outer protective casing 2, which plug retainsdust and, on the other hand, reduces the rate of fiow of the air into orout of the aneroid capsule 3 in the case of any too sudden changes ofaltitude of the aircraft.

The upper end of the casing I is closed in known manner by a sealingstopper or partition 22, through which the sealed channels 4. I3, l4already described, and the sealed shaft 9 of the pointer ID are passed.4

In Fig. 4 is illustrated the operation of the valve IS with the aid ofan auxiliary aneroid capsule 23, which is also arranged in the casing I,with suitable alteration of the arrangement of the control rod Hi. Thiscontrol rod may have, with this embodiment, also a certain amount ofplay, up to the widest expansion of the aneroid capsule 23, before itbegins to act on the valve body IS on the seat l8. The aneroid capsule23 communicates with the outer atmosphere by aid of the small tube 25. v

I claim:

1. In a rate-of-climb indicator, an air-tight casing, an an'eroidcapsule mounted within said casing, displacement indicating meansmechanically connected to said aneroid capsule for indicating themagnitude of the displacement thereof under different applied pressures,a small tube passing through said casing and connected to the interiorof said aneroid capsule and at all times connecting the interior of saidcapsule to the atmosphere without said casing, a capillary tube passingthrough said casing and connecting the interior thereof with theatmosphere without said casing, a relatively large relief passagepassing through said casing and connecting the interior thereof with theatmosphere without said casing, a relief valve mounted for controllingsaid relief passage and being normally resiliently urged into the closedposition, and connecting means positively connecting said indicatingmeans to said relief valve for opening said relief valve when saidindicating means has been actuated into a predetermined position,whereby the pressure within said casing outside of said capsule ismaintained below a predetermined maximum differential with respect tothe air without said casing.

2. In a rate-of-climb indicator, an air-tight casing comprising a flatclosing wall, an aneroid capsule mounted within said casing, a pointershaft passing through said closing wall, a pointer carried on said shaftoutside of said casing, a protective housing surrounding said casing andhaving a' passage in its side connecting with the outer atmosphere, ananeroid capsule mounted within said casing, mechanical connecting meansconnecting said capsule to said shaft for rotating said shaft as saidcapsule is deformed, a small tube passing through said closing wall andconnected to the interior of said capsule and at all times connectingthe interior of said capsule through said housing to the atmospherewithout said housing, a capillary tube passing through said closing walland connecting the interior of said casing through said housing to theatmos phere without said housing, a relatively large relief passagepassing through said closing wall and connecting the interior of saidcasing through said housing with the atmosphere Without said housing, arelief valve mounted for controlling said relief passage and beingnormally resiliently urged into closed position, and actuating meanspositively connecting said shaft and said connecting means to saidrelief valve for opening said relief valve when said shaft and saidpointer'have been actuated into a predetermined position, whereby thepressure within said casing outside of said capsule is maintained belowa predetermined maximum dilferential with respect to the atmospherewithout said casing.

RUDOLF ROUDNICKY.

